Site address is the location that will be geocoded by the system, without it you won't be able to schedule and order.
If you are using the PIP and interfacing with CCB they will send down what they call the service address but if you are using
the PIP then the PIP will take this address and convert it to a site address for you.
That means that the Service address of XML on MWM will be blank and the site address will be filled.
Keep this in mind when you are interfacing with CCB.

If you are not interfacing with CCB then you definitely need to make sure that the host sends you the site address XML.
It can also send the service address XML if it wants (this is the mailing address of the customer...or whatever else you want)
but it is optional. Site address should indicate where the work is.